Excellent advice as usual HHI Golf Guy.
It is not just Google that SERPS have been fluctuating in. I have noted the same in Yahoo and MSN.
And is seems that Yahoo is only doing it with some keyword phrases but not all.
Let me add to your advice that it is always good to back up your site BEFORE making any changes. If in fact you jumped the gun or a search engine reverts to an earlier filter or algorithm you can restore your back up.
~Mack